The successful operation of any flow injection analysis (FIA) system requires injection of a well-defined sample zone into the analyzer channel, where the zone disperses in a controlled manner on its way towards and through the detector to be measured upon (cf. U.S. Pat. Nos. 4,022,575; 4,177,677; 4,224,033; 4,314,824; 4,227,973; and 4,315,754, and U.S. patent applications Ser. Nos. 48,002; 296,256; 320,483; and 385,049). The injection devices designed for this purpose so far can be divided into two categories: (a) volume based injection; and (b) time based injection, or a combination thereof. In category (a) the injection is based on the physical entrapment of sample solution into a geometrically well-defined volumetric cavity and subsequent transfer (injection) of the thus formed sample zone into a nonsegmented carrier stream (cf. the above mentioned FIA monograph and U.S. Pat. Nos. 4,177,677 and 4,224,033). Category (b) is based on aspiration of sample solution at a constant flow rate for a fixed period of time into a well-defined section of a flow through channel, from where the metered sample zone is injected into a nonsegmented carrier stream by a combination of hydrostatic and hydrodynamic forces--the socalled hydrodynamic injection procedure (cf. U.S. patent application Ser. No. 385,049).